Still at it
Still chasing this demon around inside the bike, but here's the latest...
VALVES ARE SO TIGHT
Yesterday, I checked valve clearances... SUPER TIGHT!
- Intake clearances were 0.10mm and 0.08mm (spec is 0.10-0.20mm)
- Exhaust clearances were <0.04mm!!! (spec is 0.15-0.25mm)
Would this correlate with my symptoms? I've ordered new shims, and will obviously get this back into spec asap.
I pulled the exhaust pipe, planning to replace the exhaust gasket (#11060-1108). This went in new in Honduras not so long ago. Shocker. There was nothing left of it. Literally nothing. I thought it must have crushed into place so well that I was missing it, but after crawling around under the bike and scratching at it for a while, I'm convinced that it's just not there. I assembled this myself in Honduras, and I know I put one in. It was the standard OEM copper-looking one. Do these disintegrate?? Both nuts were tight and the exhaust pipe didn't have any wiggle until I loosened the nuts to remove it. What the heck?
I also noticed a lot of very dry, jet black build up inside the exhaust pipe, and inside the engine where the two connect. Not enough to restrict airflow, but impossible not to notice. Does this tell me anything obvious? And should I be trying to clean this stuff out? Swab a finger around inside the engine or exhaust pipe and it comes out black!
FUEL LINE NOT FULL?
I've suspected that the vacuum activated petcock in the tank might be getting stuck, restricting gas flow to the carb. To test this, I removed the plumbing inside the petcock to make it a direct gravity feed. Symptoms persisted. One thing I noticed thanks to a new, clear rubber fuel hose, is that gas does not ever fill the hose completely. Is this normal? There is no in-line filter involved, just a straight 1/4 inch tube from gravity-fed petcock down into the carb. Gasoline fills the bottom few inches of the hose right before the carb, but never the upper section. What to make of this? Something to pursue here?
FLOAT BOWL VENTS
Paul, with regards to the float bowl vent line, I'm pretty sure that's not the culprit. I've routed it every which way at various times, or pulled it off completely. No change. Although I love the trick of cutting vent hoses at an angle to prevent then sucking onto things. Nice!
If anyone read this far, you're probably a crazy person. And I can't thank you enough. Let me know if you've got any advice.